Taiwanese Utility Model Patent No. M365850 discloses a conventional driving device for a hub assembly of a bicycle. The driving device includes a stationary ring that is mounted fixedly in the hub assembly, a ratchet ring, and a pawl seat. The ratchet ring is removably engaged with the stationary ring, and has an inner ring surface that is formed with a plurality of angularly spaced-apart ratchet grooves. The ratchet grooves are uniform but asymmetrical.
The pawl seat is connected to a sprocket in a manner that the pawl seat and the sprocket are molded as one piece. The pawl seat has an outer surrounding surface, and a retaining unit formed in the outer surrounding surface.
The retaining unit has a plurality of angularly spaced-apart retaining grooves. Each of the retaining grooves has a central section that has an opening, and first and second retaining sections that are connected respectively to circumferentially opposite ends of the central section. For each of the retaining grooves, the first retaining section is engaged with a pawl member that has a claw end extending through the opening, and the second retaining section retains a resilient member for biasing the claw end of the pawl member to engage a corresponding one of the ratchet grooves of the ratchet ring such that the ratchet ring is rotatable only in a single direction.
In order to enable the ratchet ring to rotate in the opposite direction instead, the ratchet ring has to be removed from, and then reengaged with the stationary ring at a flipped orientation, and the pawl member and the resilient member in each of retaining grooves have to switch places to engage with the flipped ratchet ring properly. The need to disassemble and reassemble the driving device for the purpose of changing rotational direction is rather cumbersome.